1. Field of the Invention
The present invention relates to an optical pickup device equipped with a lens tilt adjusting mechanism for adjusting the tilt of an objective lens with respect to an optical recording medium.
2. Description of the Related Art
Some kinds of optical pickup device realize satisfactory reproduction performance and recording performance by collecting emitted light from a light source on an optical recording medium with an objective lens, adjusting the tilt of the objective lens with respect to the optical recording medium based on a result of detecting the reflected light from the optical recording medium, and maintaining an optical axis of the exit light from the objective lens perpendicular to the optical recording medium. The lens tilt adjusting mechanism arranged in such optical pickup device includes that which adjusts the tilt of the objective lens through extending and contracting operation of a piezoelectric element as disclosed in Japanese Unexamined Patent Publication No. 2003-115121 and Japanese Unexamined Patent Publication No. 2000-298855.
The lens tilt adjusting mechanism of Japanese Unexamined Patent Publication No. 2003-115121 is configured by a lens attachment part arranged in a cylindrical form in a lens holder, a plurality of piezoelectric elements arranged on a step surface on the inner side of the lens attachment part, and a rubber cap attached to the lens attachment part. The lens holder is a movable part of an actuator that magnetically moves the objective lens in a tracking direction and a focusing direction. The cap presses the objective lens arranged on the piezoelectric element from above (optical recording medium side) to maintain a state in which the piezoelectric element is sandwiched between the lens attachment part and the objective lens. With such configuration, the objective lens is tilted with respect to the optical recording medium and the lens holder by changing the applied voltage to each piezoelectric element and extending or contracting each piezoelectric element, thereby adjusting the tilt. A spherical surface and a spherical surface receiving part are arranged on the objective lens and the lens attachment part respectively at their contact position so that the objective lens rotates with the vicinity of a focus on the optical recording medium side as the center in time of tilt adjustment.
The lens tilt adjusting mechanism of Japanese Unexamined Patent Publication No. 2000-298855 is configured by a lens holder for holding an objective lens, a plate spring, an objective lens actuator base for supporting the lens holder by way of the plate spring, an objective lens actuator base holding part arranged on an optical head base, a spherical body and a coil spring freely fitted in a pass-through hole formed in the holding part, a blocking member for blocking the other side of the pass-through hole, and a plurality of piezoelectric elements for joining the objective lens actuator base and the optical head base. The spherical body is connected to the end of the objective lens actuator base inserted from the one side of the pass-through hole. The coil spring presses the spherical body towards the objective lens actuator base side in the pass-through hole. Thus, the objective lens actuator base holding part rotatably holds the objective lens actuator base so as to be rotatable in a direction of three-degree of freedom. With such configuration, the objective lens tilts together with the objective lens actuator base, the plate spring, and the lens holder with respect to the optical recording medium by changing the applied voltage to each piezoelectric element and extending or contracting each piezoelectric element, thereby adjusting the tilt.